Refactor MQTT client loop implementation to allow easier integration with third party event loops (#115)

* Refactor MQTT client loop implementation

This refactoring add a loopOnce method to MqttClient class. This method allows the MQTT client implementation to be integrated to an event loop (like ReactPHP - Ratchet).

* Update loopOnce documentation

* Add method to interface, refactor and reformat code

Co-authored-by: Marvin Mall <marvin-mall@msn.com>

Author: Alex6092

src/Contracts/MqttClient.php

@@ -8,6 +8,7 @@
 use PhpMqtt\Client\Exceptions\ConfigurationInvalidException;
 use PhpMqtt\Client\Exceptions\ConnectingToBrokerFailedException;
 use PhpMqtt\Client\Exceptions\DataTransferException;
+use PhpMqtt\Client\Exceptions\InvalidMessageException;
 use PhpMqtt\Client\Exceptions\MqttClientException;
 use PhpMqtt\Client\Exceptions\ProtocolViolationException;
 use PhpMqtt\Client\Exceptions\RepositoryException;
@@ -143,11 +144,32 @@ public function interrupt(): void;
      * @param int|null $queueWaitLimit
      * @return void
      * @throws DataTransferException
+     * @throws InvalidMessageException
      * @throws MqttClientException
      * @throws ProtocolViolationException
      */
     public function loop(bool $allowSleep = true, bool $exitWhenQueuesEmpty = false, int $queueWaitLimit = null): void;
 
+    /**
+     * Runs an event loop iteration that handles messages from the server and calls the registered
+     * callbacks for published messages. Also resends pending messages and calls loop event handlers.
+     *
+     * This method can be used to integrate the MQTT client in another event loop (like ReactPHP or Ratchet).
+     *
+     * Note: To ensure the event handlers called by this method will receive the correct elapsed time,
+     *       the caller is responsible to provide the correct starting time of the loop as returned by `microtime(true)`.
+     *
+     * @param float $loopStartedAt
+     * @param bool  $allowSleep
+     * @param int   $sleepMicroseconds
+     * @return void
+     * @throws DataTransferException
+     * @throws InvalidMessageException
+     * @throws MqttClientException
+     * @throws ProtocolViolationException
+     */
+    public function loopOnce(float $loopStartedAt, bool $allowSleep = false, int $sleepMicroseconds = 100000): void;
+
     /**
      * Returns the host used by the client to connect to.
      *

src/MqttClient.php

@@ -641,29 +641,7 @@ public function loop(bool $allowSleep = true, bool $exitWhenQueuesEmpty = false,
                 break;
             }
 
-            $elapsedTime = microtime(true) - $loopStartedAt;
-            $this->runLoopEventHandlers($elapsedTime);
-
-            // Read data from the socket - as much as available.
-            $this->buffer .= $this->readAllAvailableDataFromSocket();
-
-            // Try to parse a message from the buffer and handle it, as long as messages can be parsed.
-            if (strlen($this->buffer) > 0) {
-                $this->processMessageBuffer();
-            } elseif ($allowSleep) {
-                usleep(100000); // 100ms
-            }
-
-            // Republish messages expired without confirmation.
-            // This includes published messages, subscribe and unsubscribe requests.
-            $this->resendPendingMessages();
-
-            // If the last message of the broker has been received more seconds ago
-            // than specified by the keep alive time, we will send a ping to ensure
-            // the connection is kept alive.
-            if ($this->nextPingAt() <= microtime(true)) {
-                $this->ping();
-            }
+            $this->loopOnce($loopStartedAt, $allowSleep);
 
             // If configured, the loop is exited if all queues are empty or a certain time limit is reached (i.e. retry is aborted).
             // In any case, there may not be any active subscriptions though.
@@ -681,6 +659,36 @@ public function loop(bool $allowSleep = true, bool $exitWhenQueuesEmpty = false,
         }
     }
 
+    /**
+     * {@inheritDoc}
+     */
+    public function loopOnce(float $loopStartedAt, bool $allowSleep = false, int $sleepMicroseconds = 100000): void
+    {
+        $elapsedTime = microtime(true) - $loopStartedAt;
+        $this->runLoopEventHandlers($elapsedTime);
+
+        // Read data from the socket - as much as available.
+        $this->buffer .= $this->readAllAvailableDataFromSocket();
+
+        // Try to parse a message from the buffer and handle it, as long as messages can be parsed.
+        if (strlen($this->buffer) > 0) {
+            $this->processMessageBuffer();
+        } elseif ($allowSleep) {
+            usleep($sleepMicroseconds);
+        }
+
+        // Republish messages expired without confirmation.
+        // This includes published messages, subscribe and unsubscribe requests.
+        $this->resendPendingMessages();
+
+        // If the last message of the broker has been received more seconds ago
+        // than specified by the keep alive time, we will send a ping to ensure
+        // the connection is kept alive.
+        if ($this->nextPingAt() <= microtime(true)) {
+            $this->ping();
+        }
+    }
+
     /**
      * Processes the incoming message buffer by parsing and handling the messages, until the buffer is empty.
      *